1. Field of the Invention
The present invention is directed to centrifugal casting equipment having a vacuum assist.
2. Description of the Prior Art
Centrifugal casting techniques rotate the molds containing the casting cavities. The cavities are displaced from the axis of rotation so as to rotate about the axis. The centrifugal forces generated by this rotation drives the casting material into the cavities.
A typical casting system of this type employs molds comprised of two discs of silicone or organic rubber. Models of the items to be molded are placed between the mold discs. The mold discs are then placed in a vulcanizing machine. Pressure and heat are applied to the molds to vulcanize the rubber and form it around the patterns.
After curing, the molds are separated and the patterns removed. Runners are cut from a central sprue of the molds to the edge of each cavity.
The molds are then reassembled and placed in a centrifugal casting machine. After the casting machine has begun spinning, the casting material, such as precatalyzed resin or low temperature metal alloy, is poured in the central sprue. The casting material is thrown into the mold cavities by the centrifugal force where it solidifies. The mold halves are then separated and the castings removed.
While the technique of centrifugal casting has been found to be highly satisfactory, several shortcomings have been noted. It may be difficult to insure that the air displaced by the casting material can escape the cavity. While vents may be provided to the cavity, air can still become trapped in undercuts preventing formation of perfect castings. The turbulence of the casting material and air in the cavity often results in internal voids in the casting.